A new study claims that there's a "recipe" that raises the odds of a teen becoming sexually active early — and the more ingredients (low self-esteem, not feeling close to parents, lots of TV), the more likely a teen is to have sexual relations by the age of 15. Janet Shibley Hyde, a psychologist at the University of Wisconsin-Madison and co-author Myeshia Price conducted a two-year study of 273 children and used anonymous surveys."By 15," they write, "one out of five boys had participated in oral sex and about one in 10 said they'd had intercourse; the numbers were somewhat lower for girls. (Because the teens were mostly middle class and white, they had lower rates of sexual experience than the U.S. average.)"

Each risky factor raised the odds of sexual activity by 44%. Boys with more advanced puberty development started sex early. Teens with low self-esteem may start sex to boost their self-images or gain popularity, Price speculates. Defiant kids with attention-deficit hyperactivity disorder, those whose parents had little education or those who regularly watched certain types of TV also tried sex sooner.

What's the harm in disaffected, TV-addicted youth screwing each other? Well, kids who start having sex early have more partners than those who wait, and they're much more likely to get pregnant or catch a sexually transmitted disease, says Bill Albert of the National Campaign to Prevent Teen and Unplanned Pregnancy.

So what shall we do? Fight at the source? How do we encourage parents to spend more time with teenagers? How do we limit the amount of TV teens watch? How do we manage teenage self-esteem? And how do we keep teenage boys from giving teenage girls chlamydia in record numbers?